The present invention relates to a double acting valve unit for a hydraulic system.
A known production tractor hydraulic system includes a charge pump which supplies hydraulic fluid to a variable displacement piston pump and to a clean oil reservoir. It would be desirable to maintain at least a certain desired minimum charge pressure at the inlet to the piston pump, and to allow the free flow of oil from the clean oil reservoir to the piston pump during conditions when the piston pump requires a high volume of oil, such as when the piston pump is supplying oil to a single acting cylinders or a hitch cylinder during hitch operation.
Previously, this has required two separate valve devices, such as a conventional check valve with a parallel bypass orifice. A simpler, more compact valve unit is desired.